In a wireless network, a hybrid automatic repeat request (HARQ) protocol is used to ensure high reliability and high data transmission efficiency of the wireless network. The HARQ protocol combines a forward error correction (FEC) scheme and an automatic repeat request (ARQ) scheme.
FIG. 1A illustrates a block diagram 100 of a prior art HARQ burst 120. When data is to be sent from a sending station to a receiving station in a wireless network, the data is sent in the form of medium access control (MAC) packet data units (PDUs), or sub-packets 110. The MAC layer of the sending station concatenates the PDUs 112, 114, 116, and 118 and the physical (PHY) layer of the sending station adds a preamble 122 to the concatenated PDUs 112, 114, 116, and 118 to form a HARQ burst 120 for transmission. The PDUs 112, 114, 116, and 118 are divided or partitioned into the FEC blocks 124, 126, and 128 by the PHY layer of the sending station.
The downlink (DL) throughput of the HARQ protocol used in a station may be limited to a maximum limit to guarantee that the throughput of the HARQ protocol does not exceed the buffering capabilities of the station. FIG. 1B illustrates two scenarios 150 of the memory state of a buffer in a prior art station. The first scenario, where there is no overflow of memory 160, occurs when the buffer in the station has sufficient free memory space 166 to store a HARQ sub-burst 170 that fails a cyclic redundancy check. The HARQ sub-burst 170 may be a retransmission of the same burst that has been stored in the station as the HARQ sub-bursts 162 and 164.
To increase the throughput of the HARQ protocol used in a station, the size of each HARQ sub-burst can be increased. However, increasing the size of each HARQ sub-burst has a drawback because the station may experience more memory overflows in its buffer. This is illustrated in the second scenario, where there is an overflow of memory 180, that occurs when the buffer in the station has insufficient free memory space 186 to store the HARQ sub-burst 170 that fails a cyclic redundancy check. The station therefore aborts storing the HARQ sub-burst 170 and clears the HARQ sub-burst 170.
The current HARQ protocol implementation does not allow the throughput of the HARQ protocol to be increased or to decrease the number of occurrences of memory overflow events in a wireless network.
When transmitting an HARQ burst, the burst needs to be stored until an indication that it has been received correctly from the receiver arrives at the transmitter. In the case that the burst was not received correctly, the transmitter retransmits the stored HARQ burst. As such the longer the burst needs to be stored, usually referred to as round trip time (RTT) the lower the overall throughput can be reached.